Many people do not have that option, so Tether quickly caught on when most major exchanges offered it as a USD alternative. USDC started later, so Tether had a huge head start. I am really surprised the the big heap of rotting scam has not exploded yet.
Yes, USDC is a much safer bet.
If stablecoins were truly-backed by USD reserves, they would've been a great option for those looking into USD alternatives. Especially people living in third world countries. But that's not really the case these days with most stablecoin issuers doing shady stuff behind the scenes (adding more units to circulating supply without regular audits). USDT is certainly not an option I'd consider to secure my money long-term. Competing stablecoin USDC can be trusted due to the company's regulatory compliance. Allowing customers to exchange 1 USDC to $1 USD when it lost its peg for a short time, was a great strategy to build trust within the stablecoin itself. I doubt Tether will do the same in the future.
Besides, the US national debt keeps increasing at an alarming rate. It won't be long before the real USD weakens until it loses its position as the world's reserve currency. Once that happens, you can say bye-bye to USDT and similar coins for good. Maybe it'll be time to move to Euro-backed stablecoins?